Question

An amount of solid $N{H_4}HS$ is placed in a flask already containing ammonia gas at a certain temperature and $0.50$ pressure Ammonium hydrogen sulphide decomposes to yield $N{H_3}$ and ${H_2}S$ gases in the flask. When the decomposition reaction reaches equilibrium, the total pressure in the flask rises to $0.84$ atm. The equilibrium constant for $N{H_4}HS$ decomposition at this temperature is:
$A.0.11 \\\ B.0.17 \\\ C.0.18 \\\ D.0.30 \\\$

Answer 1

Ammonium hydrogen sulphide decomposes into ammonia and hydrogen sulphide. It is the ratio of the amount of product which is used to determine the behavior of chemicals to the reactants. At this condition the rate of forward reaction is equal to rate of backward reaction.

Complete step by step answer:
Here in the given question, if we write this in equation form we get,
Here, Ammonium hydrogen sulphide decomposes into ammonia and hydrogen sulphide.
Now when the decomposition reaction reaches equilibrium, it will add with the starting pressure with a certain pressure, let’s assume it as$x$.
So in the starting,
$N{H_4}HS \to N{H_3}(g) + {H_2}S(g)$
$0.5atm$ $\;\;\;$ $0atm$
Coming at the equilibrium state;
$0.5 + x + x = 2x + 0.5 = 0.84 \\\ \Rightarrow 2x = 0.84 - 0.5 \\\ \Rightarrow x = 0.17atm \\\$
Pressure at the ammonia is equal to the $0.5 + x$ .
$PN{H_3} = 0.5 + 0.17 = 0.67atm$
Also,
$P{H_2}S = 0.17atm$
Now for the equivalent constant,
$K = PN{H_3} \times P{H_2}S \\\ = 0.67 \times 0.17 \\\ = 0.11at{m^2} \\\$
So equivalent constant of the gas is $0.11$

So, the correct answer is Option A.

Note: The equivalent constant is the chemical reaction constant usually denoted by K that provides the relationship between the products and reactants while a reaction reaches equilibrium position.It is the ratio of the amount of product which is used to determine the behavior of chemical to the reactants. At this condition the rate of forward reaction is equal to rate of backward reaction.